Pencil Trick for Primary, Secondary, Tertiary, \u0026 Quaternary Carbon and other Atoms

how many hydrogens are attached to each of the indicated carbons in morphine? This is a topic that many people are looking for. is a channel providing useful information about learning, life, digital marketing and online courses …. it will help you have an overview and solid multi-faceted knowledge . Today, would like to introduce to you Pencil Trick for Primary, Secondary, Tertiary, & Quaternary Carbon and other Atoms. Following along are instructions in the video below:
Here from leah4scicom. And in this video. Im going to show you the pencil pencil trick to quickly and easily identify primary secondary tertiary quaternary carbon and other atomss start with carbon atoms when youre looking at a molecule if you see a carbon atom bound to other atoms the way you classify this carbon is by looking at how many carbons are attached to it in the first example.
I give you methane it doesnt have any carbons attached so it wouldnt fall under this classification. But if i take this carbon. Remove.
One hydrogen atom and swap that for a ch3. This carbon. Is now considered a primary carbon.
Atom cuz. Its attached to one of our carbon atom. If i remove.
2 hydrogen atoms and replace them. With other carbons for example methyl groups. The central carbon now being attached to two other carbon atoms is considered a secondary carbon.
If i swap three hydrogens for carbon in this. Case methyl the central atom is now attached to 123. Carbon atoms making it a tertiary carbon and last but not least if i swap each of the hydrogens for a carbon atom.
In this case 4 methyls that central carbon is attached to. 1234 carbon atoms making it a quaternary carbon. This is the simple approach.
But what happens if the molecule you see is not drawn in lewis structure. What if youre not shown a lewis structure where all the carbons are visible. What if you have to figure this out in line structure do you draw it out so that you can clearly see whats going on absolutely not this is where we introduce the pencil trick.
And this is how it works. Imagine that my stylist is the pencil. And you put it down on the carbon atom.
What you wanna do is look at that pencil point. And see what is coming out of that pencil point specifically were looking for bonds to carbon atoms. If i want to know the substitution of this carbon here all i do is put down my pencil and look at how many lines come directly from that point right.
Now. I see 1 2. 3.
3. Lines coming out of it means. 3.
Carbons attached making this a tertiary carbon. What about this one right here. I only have one line coming out of my pencil tip making it primary.
Youll notice that all terminal carbons are going to be primary. So anytime you see the end of the chain knowing that this works once it will always work these are all primary. Carbons what about this one right here from my pencil.
Tip i see 12. Making that a secondary carbon atom this trick works anytime you need to classify carbon atoms not just in a standard boring chain for example say you have a molecule with a carbocation and youre trying to determine. Which carbocation is more stable.
What do we know about carbocation stability. The more substituted. The more stable as explained in the video linked below.
So how do we figure this out your pencil down. We have two bonds coming out of it this right. Here is secondary carbocation on the right.
Put your pencil down one line coming out of it. This is a primary carbocation. Same trick applies to radicals the molecule on the left has a radical at the end if we put the pencil down one line one bond to carbon making this a primary radical and the molecule on the right.
When you put the pencil down has two lines coming out of it meaning two bonds to carbon making it a secondary radical. When it comes to an atom attached to carbon. We look at it slightly differently.
Were still looking at the carbon atom. But specifically the carbon holding that atom in question say i ask you how many primary hydrogens. We have in this molecule.
We cant look for the bonds coming from hydrogen to carbon. Because as you know hydrogen can only form one bond and in this case. Itll be one bond between carbon and hydrogen instead were looking for the number of primary carbons and then figuring out how many hydrogens are on them.
What we need is to find which carbon atom has just one line coming out of it to make it a primary carbon atom and that gives us a total of 3. Then figure out how many hydrogens sit on this carbon. The trick to figure this out is 4.
Being the total number of bonds you can have on carbon minus all of the visible bonds because these are visible to other atoms like carbon hydrogen oxygen nitrogen the rest will be hydrogen atoms for this carbon. We see one bond four minus one equals to three and we can prove it by drawing it in now.

how many hydrogens are attached to each of the indicated carbons in morphine?-0
how many hydrogens are attached to each of the indicated carbons in morphine?-0

Im only drawing this to show you but on exams youll never ever wanna waste time drawing in hydrogen atoms carbon below same thing four minus one is three and carbon on the left four minus. One is three we have three primary carbons each containing three hydrogens for a total of nine primary hydrogen atoms for secondary hydrogens. Were looking for secondary carbons.
Which when you put the pencil down has two lines coming out of it and we just have one. But how many hydrogens sit on that carbon. If we have four bonds we have four possible bonds minus.
The two visible to carbon equals. Two hydrogen atoms on a secondary carbon. And we have one secondary carbons.
Which gives us two secondary hydrogens for tertiary hydrogen. Were looking for a tertiary carbon. Thats carbon with three lines coming out of my pencil tip.
And we have one of them carbon can have 4 bonds minus 3. Bonds to carbon. Is 1 remaining for hydrogen.
Which means. 1. Tertiary carbon.
Having one hydrogen atom gives us a total of one tertiary hydrogen. We cant have quaternary hydrogen. Because if carbon can have a max of 4 bonds.
And those are all bonds to carbon. We have nowhere left for the hydrogen same thing works for alcohol. Were looking at the degree of substitution of the carbon atom specifically that is holding your alcohol.
For example. If i give you methanol methanol would not be considered a substituted alcohol. Because the carbon that is holding the oxygen is not bound to any other carbon atom.
So. If i put my pencil down. I have no lines to carbon that means.
Its not substituted at all if we look at ethanol the alcohol is attached to this carbon. There is one line to another carbon remember. Its a line to carbon.
We do not count the line to oxygen. Because were looking specifically at the carbon holding the oxygen. How many carbons is that attached to ethanol would be a primary alcohol.
If we look at isopropyl alcohol. The central carbon is holding on to the oxygen. But it also got two lines coming out to carbon atoms making this a secondary alcohol.
Tert butanol or tertiary butyl alcohol has three lines coming out of my pencil tip making this a tertiary alcohol. What if i want a quaternary alcohol can i do that i would attempt to draw the molecule backwards. I would start with my carbon atom with my pencil point attempt to draw four bonds to carbon.
But then i cant put it in alcohol because that oxygen is bound to a carbon that already has four bonds that means we have 5 bonds to carbon. Which is not allowed it violates the octet. So we have to stop at tertiary alcohols.
Alkyl. Halides are classified the same way. Say i have a molecule with multiple chlorine atoms and i want to identify the degree of substitution of each one well start with the purple coin on the right putting the pencil down i.
Have just one line one bond to carbon making. It a primary halogen or a primary alkyl halide. The green chlorine sits on the carbon.
That has three lines coming out of it three bonds to carbon making. It a tertiary chloride or a tertiary alkyl halide. Finally.
The blue chlorine sits on a carbon that has two lines two bonds to carbon coming out of it making it a secondary chloride. The last type of molecule. I wanna look at are substituted amines say ill give you a molecule that looks like this we have a ch3 bound to a nitrogen bound to an isopropyl group when looking at the carbon holding the nitrogen am.
I using the the one on the left or am. I using the one on the right. The answer is both and neither amines are different.
Were not looking at the substitution of the carbon holding the nitrogen instead were looking at the number of carbon atoms. Coming out of nitrogen that means. The pencil trick applies to the nitrogen directly.
And this would be considered a secondary amine. Not because the carbon is bound to two carbons. But because the nitrogen is bound to two carbons.
So lets classify amines starting with ammonia ammonia is not an amine because it is not bound to any carbon atoms remember the amine functional group is an r bound to an n where r can be any sort of carbon chain. The simplest amine would be a nitrogen bound to two hydrogen atoms and one carbon.

how many hydrogens are attached to each of the indicated carbons in morphine?-1
how many hydrogens are attached to each of the indicated carbons in morphine?-1

For example. A ch3. This nitrogen is bound to one carbon making it a primary amine.
If i remove two hydrogens and swap them for r groups for example. 2 methyls. The nitrogen.
When you put your pencil down on nitrogen you get two lines coming out of it towards carbon nitrogen is bound to two r groups making this a secondary amine if i replace all 3 hydrogen atoms with. Carbon when i put my pencil. Down i.
Get 12. 3. Lines.
Coming out of nitrogen to give me. A tertiary amine. And thats it thats all the hydrogen atoms to replace that doesnt mean.
I stop. There. Remember ammonia could be a base and a lone pair can grab a hydrogen.
Which means if i swap all three hydrogen atoms and the lone pair for an r group for example. 4 methyls. First thing.
I have to remember is the formal charge should minus. Has as thought in the video linked below in this case would be 4 minus. 3.
Which is equal to plus 1. This would be a quaternary amine. Which is actually called an ammonium where the ium reminds you that it has a positive on the nitrogen.
Lets put all of this together by identifying the primary secondary and tertiary carbons. As well as the substitution of the alcohols and nitrogen on this molecule. This is the molecular structure of morphine which i found on google.
Lets start high to low how many quaternary carbons. Do we have on this molecule. Were looking for anywhere.
I can put my pencil down and get 4 lines coming out of it for example this right here has two thats not quaternary this one has 3 not quaternary. Were looking for carbon with 4 bonds. Which would be this one right here and thats it moving down to tertiary.
Were looking for carbon with 3 bonds coming out of it this carbon has three bonds coming out. To carbon thats tertiary for. 123.
This one looks tertiary. But that a bound to nitrogen not carbon doesnt count this one same thing has a bound to oxygen doesnt count same thing bound to oxygen same thing and same thing looks like we have just three tertiary carbons lets move down to secondary carbon atoms now we have the ones that appear to be tertiary. But one of the bonds is to a non.
Carbon. Which a heteroatom like. Oxygen.
Or. Nitrogen. So.
We. Have. 123456789.
Ops thats not secondary. Coz its a bond to nitrogen 1011. Its 11 next.
We move on to primary carbons and we have thats not a primary carbon. Because it is not bound to another carbon atom this would be a primary carbon. Because its bound to carbon and nitrogen.
We have just one primary carbon. Now lets look at our alcohols for the alcohols. We have this oxygen sitting on a secondary carbon.
As is this oxygen that gives us two secondary alcohols and the amine remember has its own classification. Were looking at the number of bonds coming out of the nitrogen atom that would be 123. Per.
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how many hydrogens are attached to each of the indicated carbons in morphine?-2
how many hydrogens are attached to each of the indicated carbons in morphine?-2

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